Misuse of opioids and other psychoactive drugs during pregnancy is a significant problem in the US. Neonatal abstinence syndrome (NAS) affects most infants exposed to opioids in utero, although its expression is variable. Optimal treatment of NAS has not been established, with studies limited to short term outcomes, with longer term safety and efficacy undefined. In addition, genetic factors that may contribute to the severity of NAS have not been studied in newborns. The goals of this proposal are: 1) to demonstrate short and long term benefits of pharmacotherapy of NAS in the newborn period (leading to FDA approval) and; 2) to explore how genetic variations in narcotic metabolism and pharmacodynamics contribute to the pathogenesis of NAS. Results should significantly improve our understanding of NAS and elucidate how different therapeutic regimens can influence immediate and long term neurodevelopmental outcome. First, 184 term infants needing treatment for NAS will be randomized to receive either morphine or methadone in a double blind, double dummy design. It is hypothesized that morphine treated infants will require significantly fewer days in the hospital compared to methadone treated infants. Next, the effects of NAS treatment on infant neurodevelopment at 18 months of age will be assessed using the Bayley III Scales of Infant Development. It is hypothesized that morphine treated infants will have better neurodevelopmental outcome at 18 months compared to methadone treated infants. Finally, single nucleotide polymorphisms (SNPs) in the multi-drug resistance (MDR1), mu opioid receptor (OPRM1), and/or catechol-O-methyltransferase (COMT) genes (pharmacogenetic modulators of opioid action) will be analyzed and correlated with short term outcomes and neurodevelopment assessments to determine if genetic variation is important in the pathogenesis of NAS. Preliminary data does suggest that genetic variation does influence the incidence and severity of NAS. The results of these studies will enhance our understanding of the pathogenesis of NAS, define best treatment practices, promote early identification of those at highest risk for neurodevelopmental impairment, and facilitate targeted interventions to improve outcome in these high risk infants.